A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.
Steam boilers have been a useful energy source for several centuries. With a simple set up, a steam boiler combines water and heat to create pressurized steam that is easily manipulated for indoor heating, powering engines and more. There are many types of steam boilers, and each has a unique purpose. These powerful machines come with safety risks, however, including fires and explosion.
The basic set up for a steam boiler requires only a few key components. The tank is most important, because this airtight steel or wrought iron container holds the water that will be turned to steam. A heating element, which usually is gas-, oil- or coal-powered, sits below the tank. The steam valve is a small opening at the top of the tank, usually fitted to a pipe. Most high-pressure steam boilers also have a chimney that helps expel excess heat from the system.
The operation of a steam boiler is equally simple. The heating element is brought to a high temperature. The tank water eventually will begin boiling and creating steam. As steam builds, it is held in the empty part of the tank known as the dome, creating a highly pressurized environment. After the pressure reaches a certain level, which depends on the size of the boiler, the pressure is relieved by exiting out a steam valve, thus creating energy needed to power engines and heating systems.
This basic mode of operation is found in most every steam boiler, but there are a few modifications that have been created for different purposes. A superheated boiler takes the standard process and further heats the steam, increasing the temperature and energy output, and it commonly is used to rotate large turbines. Water tube boilers replace the large tank with a series of water-filled tubes that can reach boiling faster and give off more steam.
The steam boiler provides efficient energy for a variety of needs, but it also is a major safety risk. When combining high temperatures and highly pressurized situations, boiler explosions and fires can occur easily. Boiler operators traditionally monitor the tank's temperature closely in order to prevent catastrophe, and modern boilers have computerized systems to shut off heating elements. In addition, a type of closed boiler system known as the Hartford Loop constantly re-feeds the tank's water supply in order to prevent the explosive dangers of an empty tank.